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Nanospectroscopie par microscopie à effet tunnel à très basse température de jonctions supraconductrices hybrides

Abstract : We describe proximity effects in hybrid junctions made of a superconductor and a normal metal (N-S junction) or a ferromagnetic metal (F-S junction). We have measured the local density of states of these structures thanks to a very low temperature scanning tunnelling microscope (STM). Its energetic resolution is better than 18 µeV (effective electronic temperature of 106 mK). This is one of the best resolutions obtained with this kind of apparatus. Measurements were carried out with a normal or a superconducting tip, whose fabrication is described here. Concerning N-S junctions, we have studied proximity effects in a gold layer in contact to a niobium layer when the gold thickness changes. We compare the results with the one predicted by the Usadel equations. We have also studied F-S junctions. In some samples we have embedded cobalt nanoclusters in a niobium matrix. The local density of states exhibits unusual features. They are presently not explained. We also demonstrate the influence of spin-flip phenomena in proximity effects in copper-nickel layers in contact with niobium. We have to include a characteristic time tau_sf in the Usadel equations. Finally, we exhibit first experimental results on a new kind of apparatus: an Atomic Force Microscope (AFM) combined to a STM.
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Submitted on : Thursday, February 24, 2005 - 10:05:08 AM
Last modification on : Friday, December 18, 2020 - 1:34:04 PM
Long-term archiving on: : Monday, October 22, 2012 - 10:55:33 AM

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  • HAL Id : tel-00008378, version 2

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Laurent Crétinon. Nanospectroscopie par microscopie à effet tunnel à très basse température de jonctions supraconductrices hybrides. Supraconductivité [cond-mat.supr-con]. Université Joseph-Fourier - Grenoble I, 2004. Français. ⟨tel-00008378v2⟩

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